Extendible dipper with extruded portion for a backhoe arm

ABSTRACT

The invention relates to an extendible dipper assembly ( 32 ) for a backhoe arm for a construction equipment machine, said arm comprising a boom to be attached to the machine, and an extendible dipper assembly ( 32 ) articulated at the free end of the boom ( 30 ) for holding a working  38  tool, said extendible dipper assembly ( 32 ) comprising a proximal part ( 34 ) articulated to the boom ( 30 ) and a distal part ( 36 ) which is slidingly connected to the proximal part so as to form a length-adjustable dipper assembly, characterized in that at least one of the dipper parts ( 34, 36 ) comprises a rectilinear profile made by extrusion of metal, said profile having a closed cross-section around at least one inner cavity.

BACKGROUND AND SUMMARY

The invention relates to the field of construction equipment machines having a backhoe arm where a part of the arm is extendible.

Many construction equipment machines are equipped with a backhoe, that is a piece of equipment where a bucket is mounted at the end of an arm, the arm being itself mounted on a chassis of machine. The arm usually comprises at least a boom, which is articulated to the chassis through at least a horizontal axis, and very often also around a vertical axis, and a dipper which is articulated at the free end of the boom around another horizontal axis. The dipper may also be articulated with respect to the boom around a vertical axis. Each of these movements is controlled by a power cylinder, usually a hydraulic cylinder, respectively a boom cylinder for controlling the movement of the boom relative to the chassis and a dipper cylinder for controlling the movement of the dipper relative to the boom. The bucket is articulated to the dipper around another horizontal axis and is controlled by another cylinder. In a backhoe, the bucket and the arm can be controlled to pull back material towards the chassis of the machine.

In some cases, the dipper part of the arm is extendible, that is it comprises a proximal part articulated to the boom and a distal part which is slidingly connected to the proximal part so as to form a length-adjustable dipper assembly. A cylinder is in most cases provided for adjusting the relative position of the two parts of the dipper.

In most cases, the dipper is made of an elongated hollow box section made of metal. A conventional way of making a dipper is to weld together four elongated plates of metal at or near their longitudinal edges in order to form the box section.

In the case of an extendible dipper, there needs to be provided a slide mechanism connecting the two parts of the dipper in a way that the two parts may slide relative one the other along a longitudinal direction but that they are otherwise rigidly connected along all other directions. Such slide mechanism is known where one part is equipped with two parallel rails, and where the other part is equipped with a set of slides which slide on at least two opposite surfaces of each of the rails to achieve the desired sliding junction of the two parts. In some cases, the rails may be welded on the corresponding part. It is also known to have one part of the dipper which comprises an extruded U shaped rectilinear portion to which is welded another U shaped portion. The two U shaped portions are mounted upside down. The extruded welded portion may comprise rails which are formed by extrusion together with the rectilinear U shaped extruded portion. This long known fabrication technique has proven successful but needs very careful welding operations. Indeed, it is well known that welding operations, which involve localized heating and subsequent cooling of the portions to be assembled, tend to generated internal stresses in the final object which cause deformations of said object. Such deformations are unacceptable when it is required that the object is to be joined to another object through a very precise sliding connection. Therefore, such cautious welding operations which are necessitated with the known fabricating techniques of extendible dipper arms make them expensive.

It is desirable to provide a new design of an extendible dipper assembly which would allow using easier and lower cost manufacturing processes.

It is proposed an extendible dipper assembly for a backhoe arm for a construction equipment machine, said arm comprising a boom to be attached to the machine, and an extendible dipper assembly articulated at the free end of the boom for holding a working tool, said extendible dipper assembly comprising a proximal part articulated to the boom and a distal part which is slidingly connected to the proximal part so as to form a length-adjustable dipper assembly, characterized in that at least one of the dipper parts comprises, a rectilinear profile made by extrusion of metal, said profile having a closed cross-section around at least one inner cavity.

DESCRIPTION OF FIGURES

FIG. 1 is a schematic side view of a backhoe loader equipped with an extendible dipper.

FIG. 2 is a schematic perspective view of the distal and proximal parts of a length-adjustable dipper assembly.

FIG. 3 is a schematic transversal section of a length-adjustable dipper assembly, showing the sliding connection of the proximal and distal parts of the dipper assembly.

FIG. 4 is a schematic perspective view of an extruded linear profile from which a dipper part according to the invention can be made.

FIG. 5 is a cross section of the extruded linear profile shown on FIG. 4.

DETAILED DESCRIPTION

On FIG. 1 is shown a construction equipment machine 10 of the so-called backhoe-loader type. Such machine comprises a chassis 12 mounted on four wheels and a cabin 14 mounted on the chassis for receiving an operator of the machine. In front of the cabin 14, a bonnet 16 receives the machine's main engine. Such a machine therefore exhibits the main looks of an agricultural tractor. It derives its name from the fact that it carries two main pieces of equipment, namely a loader equipment 18 at the front, and a backhoe equipment 20 at the rear. The loader equipment 18 comprises essentially two loader arms 22 which are articulated on the chassis around a horizontal axis Al near the rear end of the bonnet 16 and which extend longitudinally towards the front on both sides of the bonnet 16. At the free ends of the loader arms, in front of the bonnet 16, a loader bucket 24 having a generally forward facing cavity is articulated around a horizontal axis A2.

The backhoe equipment 20 comprises a backhoe arm 26 which is articulated on the chassis 12 and which carries at its free end a working tool such as an excavator bucket 28. In the shown embodiment, the backhoe arm 26 comprises a boom 30 and an extendible dipper assembly 32. The boom 30 is articulated to the chassis around a horizontal axis A3 and around a vertical axis A4, each rotation movement being controlled by at least one actuator, usually a hydraulic cylinder. As better seen on FIG. 2, the dipper assembly 32 comprises two main parts, namely a proximal part 34 which is articulated at one end around a horizontal axis A5 at the free end of the boom 30, and a distal part 36 which is slidingly connected to the proximal part 34 so as to extend along a lengthwise axis X-X beyond the free end of the proximal part 34. The two parts 34, 36 are connected by an actuator, not shown on the drawings but usually embodied as a hydraulic cylinder, to expand or retract the distal part with respect to the proximal part, thereby adjusting the length of the dipper assembly 32. The excavator bucket 28 is articulated at the free end 40 of the distal part 34 around a horizontal axis A6.

The proximal part 34 of the dipper assembly 32 is for example a fabricated steel sheet structure which extends along the lengthwise axis X-X of the dipper assembly and which exhibits approximately the shape of a U when viewed in cross section, the U shape enclosing partially an inner space 38 which is open towards its top, at least along a substantial portion of the proximal part 34. As can be seen on FIG. 2, the distal part 36 is at least partially received within the inner space 38 of the proximal part 34, both lengthwise and in cross section. In any case, at least in an extended configuration, the free end 40 of the distal part 36 extends lengthwise beyond the free end 42 of the proximal part 34, outside of inner space 38.

As can be seen on FIG. 3, the proximal part of the dipper is fabricated with metal plates which are welded together, mainly two lateral plates 44 which extend parallel one to the other, and a cross plate 46 which extends between the two lateral plates 44. The proximal part also comprises bushes and reinforcements which are mainly made as welded add-on parts.

A backhoe loader such as the one described above is well known to the skilled man in the art and is for example commercially available as “Volvo BL 71”.

In the example shown on the figures, the distal part 36 of the dipper assembly comprises a rectilinear profile 48 made by extrusion of metal, said profile having a closed cross-section around at least one inner cavity 50. The rectilinear profile 48 is best shown on FIGS. 4 and 5 where it is represented just after its fabrication by the extrusion process. The rectilinear profile extends along the lengthwise axis X-X of the dipper assembly, and it is therefore possible to define the axis X-X as being the extrusion axis. The inner cavity 50 is closed when viewed in cross section along a plane perpendicular to axis X-X, as represented. Said otherwise, the rectilinear portion exhibits a continuous wall portion which extends around axis X-X. Therefore, the rectilinear profile is inherently very rigid, and inherently resists to flexions around any axis perpendicular to the lengthwise axis X-X, but also resists to torsion around said lengthwise axis X-X.

In the example shown, the rectilinear profile 48 encloses only one inner cavity 50 which is substantially rectangular in cross section, with rounded angles. Indeed, the rectilinear profile comprises a continuous wall made of mainly four wall portions, two lateral wall portions 52 and two cross wall portions which can be called top wall portion 54 and bottom wall portion 56. Top and bottom here simply refer to the drawings and are not to be construed as limiting the scope of the invention. The lateral wall 54 portions are parallel one to the other and the cross wall portions 56 are also parallel one to the other, but perpendicular to the lateral wall portions. Each lateral wall portion 54 is connected to the two cross wall portions 56 by a rounded wall portion, and vice-versa.

As represented on the figures, the rectilinear profile comprises two rectilinear protrusions 58 which extend each outwardly in cross section from the lateral wall portions 52 and which each form a rail for slidingly connecting the proximal part 34 to the distal part 36. In the example shown, the protrusions are located near the bottom wall portion 56. In the particular example shown, they exhibit a triangular cross section with one side being simply adjacent to the corresponding lateral wall portion, an upper side 60 perpendicular to the lateral wall portion and a lower side 62 which is slanted at approximately 45 degrees and which merges with the bottom wall portion 56. As can be seen on FIG. 2, the upper and lower side of the protrusions 58 form guiding surfaces which are deemed to cooperate with slides or rollers arranged on the proximal part so as define a sliding connection between the two parts. Both rectilinear protrusions 58 are preferably formed by extrusion together with the rectilinear profile. This of course eases considerably the assembly and the operation of the dipper inasmuch as, being obtained through the extrusion process, the protrusions have a well defined geometry and have a well defined location with respect one to the other and with respect to the other wall portions of the rectilinear profile. Thanks to the intrinsic qualities of the extrusion process, the upper and lower surfaces of the protrusions need not necessarily be further machined after extrusion to exhibit the dimensions and surface geometries required for them to function as guiding surfaces in the sliding connection between the two parts of the dipper.

In the example shown, the two rectilinear protrusions 58 are located un-symmetrically with respect to a geometric axis of the cavity. In the example shown, the cavity 52 is: symmetrical around a central axis which can be considered to correspond to the lengthwise axis X-X mentioned above. Rather than being at the level of the axis X-X, the protrusions extend near the bottom wall 56.

According to an advantageous feature, the top wall portion 54 has an increased thickness in comparison to the thickness of the bottom wall portion 56. The thickness of the top wall portion is preferably at least 25% superior to that of the bottom wall portion, but can be more than 50% superior. As a matter of fact, the bottom wall portion 56 is here represented has having approximately the same thickness as the two lateral wall portions 52 but it could in fact exhibit a lower thickness than the two lateral portions. Of course, the rectilinear profile 48 is designed so that it resists to all the stresses it will meet in operation, but the advantage of providing an excess thickness in the upper wall portion 54, i.e. the wall portion which is on the opposite to the protrusions 58 with respect to the cavity axis X-X, is that the centre of gravity of the profile, when considered in cross section, is close to the axis of symmetry of the cavity, despite the un-symmetrical locations of the protrusions 58. This allows an easier production of the profile 48 with the protrusions 58 by the known extrusion techniques.

Thanks to this feature, the rectilinear profile 48 can be made of steel having an elastic limit of at least 240 MPa, or even of at least 360 MPa. Alternatively, the rectilinear profile 58 could be made of aluminium or of an aluminium alloy.

Thanks to the proposed design, the rectilinear profile 48 is devoid of welding around its cross-section. This avoids any deformation which may be caused by a welding operation.

Of course, the rectilinear profile 48 is a base element of the distal part 32, but the rectilinear profile may be transformed to form the distal part, and the distal part may also comprise other components. At a minimum, the rectilinear profile will be cut at the right length for forming the distal part. Holes may be drilled in the profile, for example at axis A6 for receiving an articulation for the working tool. For example, such articulation holes may reinforced by the provision of bushings which may be welded on the rectilinear profile. Also, brackets may be fixed on the rectilinear profile, by welding or by other attaching means, for example for the connection of the power cylinders which control the extension of the dipper assembly and/or control the movement of the working tool.

In the example shown and described above, it is the distal, part 36 of the dipper assembly 32 which comprises a rectilinear profile 48 made by extrusion of metal according to the invention, while the proximal part is of a more conventional design. Nevertheless, The proximal part 34 of the dipper assembly 32 could also or alternatively comprise a rectilinear profile made by extrusion of metal according to the invention.

It is to be mentioned that, within the scope of the invention, the cross-section of the rectilinear profile and of its inner cavity could be other than rectangular, and could be for example in the shape of a trapeze, circle, oval, or even exhibit a more complex design, such as the shape of an X. The cross-section could also be non-symmetric, not withstanding the further un-symmetrical location of the protrusions. Also, the rectilinear profile could comprise more than one cavity defined within the closed cross section. For example the inner cavity could exhibit several partitions formed by a wall portion obtained directly during the extrusion process.

All in all, the use, of an extruded closed section rectilinear profile allows to produce more easily, more cheaply and more quickly a dipper assembly which exhibits superior performance, especially due to the fact that the extrusion process minimizes the residual constraints which are inherent to the conventional fabrication process based on welded plates.

The invention has been described in the context of a backhoe arm to be mounted on a backhoe-loader, but it would obviously be applicable in any type of backhoe arm, for example for use on an excavator. 

1. Extendible dipper assembly for a backhoe arm for a construction equipment machine, the arm comprising a boom to be attached to the machine, and an extendible dipper assembly articulated at the free end of the boom for holding a working tool, the extendible dipper assembly comprising a proximal pact articulated to the boom and a distal part which is slidingly connected to the proximal part so as to form a length-adjustable dipper assembly, wherein at least one of the dipper parts comprises a rectilinear profile made by extrusion of metal, the profile having a closed cross-section around at least one inner cavity.
 2. Extendible dipper assembly according to claim 1, wherein the rectilinear profile comprises at least one rectilinear protrusion which extends outwardly in cross section and which forms a rail for slidingly connecting the proximal part to the distal part, the rectilinear protrusion being formed by extrusion together with the rectilinear profile.
 3. Extendible dipper assembly according to claim 2, wherein the rectilinear protrusion comprises at least one guiding surface which cooperates with a slide or a roller of the other part of the dipper for slidingly connecting the proximal part to the distal part, the guiding surface being directly obtained through the extrusion process.
 4. Extendible dipper assembly according to claim 2, wherein the rectilinear profile comprises two rectilinear protrusions which are located un-symmetrically with respect to a geometric axis of the cavity, and in that the rectilinear profile comprises at least one wall portion which is located substantially opposite the protrusions with respect to the cavity axis, the opposite wall portion having an increased thickness in comparison to at least one other wall portion of the profile.
 5. Extendible dipper assembly according to claim 4, wherein the rectilinear profile is substantially rectangular with two lateral wall portions extending along its longest dimension, a bottom wall portion and a top wall portion, in that the protrusions are located near the bottom wall portion, and in that the top wall portion has an increased thickness in comparison to the thickness of the bottom wall portion.
 6. Extendible dipper assembly according to claim 1, wherein the rectilinear profile is made of steel having an elastic limit of at least 240 MPa.
 7. Extendible dipper assembly according to claim 1, wherein the rectilinear profile is made of steel having an elastic limit of at least 360 MPa.
 8. Extendible dipper assembly according to claim 1, wherein the rectilinear profile is made of aluminium or of an aluminium alloy.
 9. Extendible dipper assembly according to claim 1, wherein the rectilinear profile is devoid of welding around its cross-section.
 10. Extendible dipper assembly according to claim 1, wherein the distal part of the dipper comprises a rectilinear profile made by extrusion of metal, the profile having a closed cross-section around at least one inner cavity. 